Hello, Semwolf.
Unhappily, after decompilation the map presents unconfigured textures and some brushes too.
See images from map 70 addon Iron Cross below:
Brushes unconfigured:
Textures misaligned:
Conclusion: The map needs to be reconstructed and this task requires a lot of patience and perseverance.
There is not an efficient method to accelerate this reconstruction.
If you get to contact the map's author and get the source map, i think this be a efficient method, once you show interest in converting these maps to the single player mode.